Fig. 7. The multi-component feedback circuit regulating the σ^G regulon.

σ^G, encoded by the sigG gene, stimulates the transcription of sigG and spoVT, encoding the DNA-binding protein SpoVT. SpoVT in turn stimulates or represses the expression of other σ^G-controlled genes, including activating ylyA and repressing spoVT and sigG. YlyA interacts with RNA polymerase and stimulates σ^G-dependent gene expression. Through an unknown mechanism, spoVT gene expression is upregulated in cells lacking YlyA (indicated by the dashed repressor symbol from ylyA to spoVT), resulting in the upregulation of genes activated by SpoVT (e.g. sspB and spoVA) and downregulation of genes repressed by SpoVT (e.g. gerB).